Gas plating using nitrous oxide



United States Patent GAS PLATING USING NITROUS OXIDE Leo J. Novak and Howard J. Homer, Dayton, Ohio, as

signors to The Commonwealth Engineering Company of Ohio, Dayton, Ohio No Drawing. Application May 9, 1956 Serial No. 583,637

16 Claims. c1. 1 17--1o7 Another object'is to providea method of gas' plating materials to metallize' them wherein the plating isfca'rr'ied outin the presence ofa brightener whichaltersfjthe'p hys' ical characteristic of the deposit'whereby themetalc'o'at ing is smooth and bright;

A further object is to provide a method of gas plating which-produces metal deposits: having increasedlight re flectanceas compared to that exhibited'byordinary: gas plating methods and which produce'dull; non-reflective metal-deposits.

Another object is to produce a smooth, even metal coating, e. g. nickel, that canbesubsequently electroplated with copperwithout'the necessity "of first abrading the surface. a 1 Stillianother object of the invention-is to'provide metal coatings whichexh'ibit a mirror like reflectahce by gas plating using metal'comp'ounds such as"me'tal carbonyls and-the. like, which are heat-decomposed incontact with th'e'heated surface to be metal coated, the 'surfacebeing heatedto a temperature suflicient to cause the gaseous metal compound to decompose andjthe metal constituent to deposit "on the heated surface. f

' and other objects andadvantages will be apparout to those skilledin the art from the"following"d'e scription;

Briefly, inaccordancewiththis' invention; it has been discovered that by carrying out gas'plating employing a heat-decomposable metal compound, e. g., metal carbonyl and a volatile compound containing. nitrogen, that metal deposits which are smooth and mirror-like are produced. The method has been found to be" particularly useful in gas plating nickel from nickelcarbonyl'to produce smooth, bright metal deposits.

' Gaseous nitrogen compounds found to be etfe'ctive brighteners in gas plating metal deposits are the volatile amines, for example ammonia, orcompounds which re lease-NH .on being heated such as methanamine (hexamethylene tetramine). Nitrous oxide (N 0) gas also hasbeen found to produce bright'metal deposits. Small quantities 'of these'compoun'ds need only be used; For

example 0.5 to 15% by'volume of the brightener in the gaseous plating mixture has been found to be effective.

2,859,132 Patented Nov. 4, 1958 Bi'ight'me'tal depositsiiiay' be obtained from 0.5 to 15% by volume ot the brightener but the best results are obtained with nickel carbonyl when the gaseous nickel carbonyl plating gas contains about 10% by volume of brightener such as nitrous oiiide or sublimed methenamine or ammonia. i 1

While the reason for the enhanced results obtained using metal carbonyl containing these gaseous compounds as brighteners hasnot .been'establishedit is believed that the presence of nitrogen as NH or N 0 provides a reducingand; deposition-inodify ingatmosphere duringgas plating which results in the production of bright m etal deposit. It is also believed that the presence ofthe brightenercompoundproduces a grain refining effect. Any one or all of these factors may account for ,the'production of thehighly reflective metal deposits using metal carbonyl-'andth'e' gaseous nitrogenous brightener; The bright metal gas'plating depositma'y' be" produced on various materials, e. g., fibers made of glass, wire or the lil i'e inorganic material as well as synthetic fibers, filaments or t fabrics, made of rayon, nylonand the like.

Met'alsFto be deposited may be introduced as gaseous nietal carbonyls or vaporized solutions of certain of the metal carbonyls in readily vaporizable solvents (e. g. petroleum ether) also nitroxyl compounds, nitrosyl carbonyl's, metalhydrides, metal alkyls, aryls or aralkyls, metal halides, and the like. Illustrative compounds of the carbonyl type are carbonyls' offnick el, iron, chromium, molybdeiiiim," tungsten, cobalt, a nd ruthen i l d Illustrative compounds of other groups are the nitroxyls,

such as copper nitroxyl, nitrosyhcarbonyls, for example, cobalt'nitrosyl' carbonyl; hydrides'," such as 'antim tinyghydride, tin hydride; metal alky-ls; an'cIlialides" siicli a chroniylchloride; andcarboriyl halogens; for example, osmium carbonyl bromide, ruthenium carbonyl chloride, and the like. I Each material from which a metal may be plated: has a temperature at which decomposition is complete. However, decomposition may take place slowly atJa lower temperature or while vapors are being raised intempera ture through some particular range. For example, nickel carbonyl completely decomposes at a temperature in the range of 375 F to 400 F. Howeven nickel carbonyl starts to decompose slowly'at about 'F. and therefore decomposition continues during the time of heating from 200 FQto 380 F. p j j' A large number of the metal 'carbonyls and hy'drid'es' may be efiectively and eificiently'decomposed at a temperature in the range of 350 F. to 450 F. Whenworking 'with' most metal carbonyls we'prefertooperate in a temperature range of from 375 F. to 425 F. I

Heating of objects to temperatures in the aboverange may be accomplished in many ways depending up'o'fithe' type of object being plated. If the object is stationary, the object may be set on a resistance heater or so.cal1ed hot' p'la'te. If the object is moving, it may'behea'ted by passing'over resistance heaters, or by infraredlight'; or by'pas'sage of-electricity therethrough either of standard or-high frequency or like means.

The material to be coated, where necessary, is cleaned of-foreignmatter prior to gas plating,-this maybe ef-' fected mechanically or chemically, or by employing both, depending upon the material being gas plated. Where refractory fibers, such as glass are to be ga's'plated with metal, the same may be effected by subjecting the hot glass fiber as it is continuously drawn' from' a molten batch of glass into fibers. In the gas platingxor organic fibers or material made of such fibers, it, of course, is

necessary to control the temperature and time of heat- (NH was used as the brightening agent to produce a ing the fibers whereby the gas plating can be'attained bright nickel deposit. without injuring the material. Example IX Inert carrier gas such as carbon dioxide helium, nitrogen and hydrogen which is free of oxygen preferably i 5 In this example a panel or board molded from synused as a carrier gas, generally making up f o b t thetic resin condensation product of ethylene glycol and 25% to 70% of the gaseous medium of the gas plating telephthallc acld 2 Mylar) sandblastefl and chamber, the remainder being gaseous metal carbonyl then Vapor degreased y the appllctlon 0f trltfhlorand-nitrous oxide.

v I f, ethylene. The thus cleaned surface is sprayed lightly Theinventio i f -th ill t ated-b h f llowjh with a solution consisting (by we1ght) .of parts conexamples. i centrated ammonium hydroxide (hIH OH), 15 parts I r i E l l' I I formalin (27% formaldehyde solution) and 80 parts I e ethyl alcohol. Thereafter the panel was placed in the Copper dlscs .wlre brushed to clean the surface gas plating chamber and heated to 280 F. and the cham- The discswere positioned on the hot plate and heated 15 her purged with carbon dioxide. The heated panelwas to a temperature of approximately 400 F. Into the housing was fed a'mixture-of vaporous nickel carbonyl admixed with nitrous. oxide (10% by volume being ni- 1 trous oxide), and argon gas, the carbonyl being present in theproportions of approximately 5 ozs. of carbonyl per cubic foot of argon.

The copper discs were plated in accordance with standard operating procedure of passing approximately 3 cubic feet of gas mixtureper hour through ,the housing, for a period of 2 minutes, at the end of which time a plating of 0.0012 inch of nickel was obtained which was bright and light reflective.

I Example II Glass fiber treated as in the previous operation is positioned on the hot plate and an identical gas mixture fed to the chamber. Inside the chamber the gas was maintained at a temperature of approximately 125 F. by the-coolant. However, the gas circulated in the housing at a rate of about 60 feet per second due to the operation of the fan. The plating time was 2 minutes, as in Example I, and a smooth bright nickel deposit is produced. 1

I Example 111 Rayon fiber is treated as described in Example II, .but maintaining the temperature of plating at between 180- 190 F., and a nickel plated fiber is thereby produced.

Example IV The process of Example I'is repeated using molybdenum carbonyl gas in place of nickel cabonyl and gas plating in the presence of nitrous oxide to produce a bright smooth deposit of the metal.

Example V The process of Example I'is repeated using chromium carbonyl instead of nickel carbonyl and gas plating concurrently in an atmosphere containing nitrous oxide to produce a bright deposit of chromium.

Example VI In this example the gas plating of nickel on glass fibers was carried out as described in Example I, except in place of nitrous oxide, there was substituted sublimed or gaseous methenamine.

' Example VII In this example a sheet or panel (2" x 4") made of then gas plated for six minutes with nickel carbonyl, the latter flowing at 2140 cubic centimeters per minute into the plating chamber. r

The plated panel had a bright reflective surface finish.

Example X A resin board was sandblasted and cleaned and gas" plated using nickel carbonyl and brightener solution spray of formalin andammonia in ethyl alcohol as described in Example IX. In this instance the plating gas mixture was diluted 50/50 by volume with carbon dioxide. .A bright metal deposit was obtained after six minutes gas plating similarly as in Example IX.

Example Xl Gas plating of nickel on resin board was carried out I silvery coating deposit of nickel was obtained.

Example 1 In this. example, a resinpanel was cleaned and gas plated as describedin ExampleIX, utilizing a plating temperature of 300 F.-

The plating gas'consisted of a mixture flowing into the plating chamber per minute 'of' 4800 cclargon gas 23 cc. ammonia gas'(NH After gas plating with the above mixture for five minutes the plated resin board was removed and exhibited a bright mirror-like deposit of nickel.

Although exhaustive tests have not been made,,there is an indication that the. compounds which function best as brighteningagent in 'gas plating are those containing nitrogen and'whichhave an affinity for oxygen, e. g..re-- I ducing compounds. A synergisticeffectis believed to' be produced by such nitrogen compounds, the same functioning bothas' a grain refiningagent and deoxidizing agent to thus prevent darkening of the uniformly fine grain deposit. -.This effect 'is further substantiated by test runs made wherein hydrogen gas was used to provide a reducing atmosphere during gas plating, but this failed to produce bright mirror-like metal deposits, and such as produced using-NH; and N 01 as brightening agents. Tests also haveshown that the use of inert gases suchas argon, helium, nitrogen, carbon dioxide, etc. are not effective as brighteners. These gases are, however, useful as carrier gases for the metal bearing gases. Further experimental runsrhave indicated that a mixture of inert gas with a deoxidizer, or reducing gas, such asthe bright ening compounds of nitrogen aforementioned Work best where a bright smooth deposit of metal is desired.

When gas plating with heavymetals, e. g. carbonyls of nickel,..chrom ium, copper, molybdenum, etc, it is not necessary to havet he plating chamber free of water vapor and in v some instances the presence ofasmallfamount of water vapor is beneficial. In the case of gas plating of light metals, such as aluminum, magnesium or lithium which readily react with water, it is necessary to provide a moisture free atmosphere in the gas plating chamber.

As a carrier gas, argon is better than nitrogen because of the tendency of nitrogen to form nitrides. Argon is also a conductor of electricity and thus assists in ionizing the gaseous metal compound during gas plating. Other relatively inert gases which may be used are neon, krypton and xenon.

It will be understood that while there have been given herein certain specific examples of the practice of this invention, it is not intended thereby to have this invention limited to or circumscribed by the specific details of materials, proportions, or conditions herein specified, in view of the fact that this invention may be modified according to individual preference or conditions without necessarily departing from the spirit of the disclosure and'the scope of the appended claims.

What is claimed is:

1. The method of gas plating bright, smooth metal coatings which comprises bringing a mixture of metalbearing vapor and a gaseous brightener compound containing nitrogen into contact with the article to'be plated, and heating the gaseous mixture to a temperature sufficient to cause decomposition of the metal bearing vapor and deposition of the metal constituent onto the surface of the article, said nitrogen-containing compound being selected from the group consisting of ammonia, methenamine, nitrous oxide, and ammonium hydroxide.

2. The method of gas plating bright, smooth metal coatings which comprises bringing a mixture of gaseous metal carbonyl and a gaseous brightener compound containing nitrogen into contact with the article to be plated, and heating the gaseous mixture to a temperature sufficient to cause decomposition of the gaseous metal car bonyl and deposition of the metal constituent onto the surface of the article, said nitrogen-containing compound being selected from the group consisting of ammonia, methenamine, nitrous oxide, and ammonium hydroxide.

3. The method of gas plating surfaces of material to provide the same with a light reflective coating of metal which comprises the steps of heating said surface to be plated to a temperature suflicient to cause decomposition of a heat-decomposable metal-bearing gaseous compound brought in contact therewith, and while thus heated contacting said heated surface with a heat-decomposable metal-bearing gaseous compound in the presence of a brightening agent, said brightening agent being a gaseous compound containing nitrogen and selected from the 1 group consisting of gaseous ammonia and nitrous oxide.

4. The method of gas plating metal onto surfaces of material to provide the same with a light reflective coating of metal which comprises the improvement step of heating the material to be plated and contacting the same while heated with vaporizable metal carbonyl admixed with nitrous oxide, said heating being suflicient to cause decomposition of the metal carbonyl and deposition of the metal onto the surface of the material.

5. The method of gas plating metal onto surfaces of material to provide the same with a light reflective coating of metal which comprises the improvement step of heating the material to be plated and contacting the same while heated with vaporizable metal carbonyl admixed with methenamine, said heating being suflicient to cause decomposition of the metal carbonyl and deposition of the metal onto the surface of the material.

- 6. The method of gas plating nickel onto surfaces of rayon fiber to provide the same with a light reflective coating of metal which comprises the improvement step of heating the rayon fibers to be plated and contacting the same while heated with vaporizable nickel carbonyl admixed with a brightener, said brightener comprising a compound of nitrogen, and said heating being suflicient to cause decomposition of the nickel carbonyl and deposiammonium hydroxide. 7. The method of gas plating molybdenum carbonyl onto surface of material to provide the same with a light reflective coating of metal which comprises the'improve ment step of heating the material to be plated and contacting the same while heated with vaporizable molybdenum carbonyl admixed with nitrous oxide, said heating being suflicient to cause decomposition of the molybdenum carbonyl and deposition of the molybdenum carbonyl onto the surface of the material.

8. The method of gas plating chromium carbonyl onto surfaces of material to provide the same with a light reflective coating of metal which comprises the improvement step of heating the material to be plated and contacting the same while heated with vaporizable chromium carbonyl admixed with nitrous oxide, said heating being suflicient to cause decomposition of the chromium carbonyl and deposition of the chromium carbonyl onto the surface of the material.

9. In the method of gas plating metals onto surfaces by bringing metal bearing gaseous compound into contact with the surface to be plated and heating said metal bearing gaseous compound to a temperature suflicient to cause it to decompose and deposit the metal constituent onto the surface to be plated, and carrying out said deposition in the presence of nitrous oxide.

10. The method of gas plating metal onto surfaces of material to provide the same with a light reflective coating of metal which comprises the improvement step of heating the material to be plated and contacting the same while heated with vaporizable metal carbonyl admixed with methenamine, said heating being suflicient to cause decomposition of the metal carbonyl and deposition of the metal onto the surface of the material, said methenamine being introduced as an aqueous solution of formaldehyde and ammonia which upon heating releases methenamine.

11. In the method of gas plating metals onto surfaces by bringing metal bearing gaseous compound into contact with the surface to be plated and heating said metal bearing gaseous compound to a temperature suficient to cause it to decompose and deposit the metal constituent onto the surface to be plated, and carrying out said depo sition in the presence of ammonia gas;

12. In the method of gas plating metals onto surfaces bringing metal bearing gaseous compound into contact with the surface to be plated and heating said metal bearing gaseous compound to a temperature suflicient to cause it to decompose and deposit the metal constituent onto the surface, to be plated, and carrying out said deposition in the presence of a gaseous compound of nitrogen which has an aflinity for oxygen, said nitrogen compound being selected from the group consisting of ammonia, methenamine, nitrous oxide and ammonium hydroxide.

13. In the method of gas plating metals onto surfaces by bringing metal bearing gaseous compound into contact with the surface to be plated and heating said metal bearing gaseous compoundto a temperature suflicient to cause it to decompose anddeposit the metal constituent onto the surface to be plated, and carrying out said deposition in the presence of a mixture of ammonium hydroxide and formaldehyde. 1

14. In the method of gas plating metals onto surfaces by bringing metal bearing gaseous compound into contact with the surface to be plated and heating said metal bearing gaseous compound to a temperature suflicient to cause it to decompose and deposit the metal constituent onto the surface to be plated, and carrying out said deposition in the presence of a spray solution consisting of a mixture by weight of 15 parts concentrated ammonium hydroxide, 15 parts formalin and parts ethyl alcohol. 

1. THE METHOD OF GAS PLATING BRIGHT SMOOTH METAL COATINGS WHICH COMPRISES BRINGING A MIXTURE OF METALBEARING VAPOR AND A GASEOUS BRIGHTENER COMPOUND CONTAINING NITROGEN INTO CONTACT WITH THE ARTICLE TO BE PLATED, AND HEATING THE GASEOUS MIXTURE TO A TEMPERATURE SUFFICIENT TO CAUSE DECOMPOSITION OF THE METAL BEARING VAPOR AND DEPOSITION OF THE METAL CONSTITUENT ONTO THE SURFACE OF THE ARTICLE, SAID NITROGEN-CONTAINING COMPOUND BEING SELECTED FROM THE GROUP CONSISTING OF AMMONIA, METHENAMINE, NITROUS OXIDE, AND AMMONIUM HYDROXIDE. 